The Backyard Cat product is a weighted bag that hangs from a little harness and trains your cat not to jump. It also trains your cat to be depressed and miserable. It looks like torture and costs $18 - $22 depending on the size of your cat. It was designed specifically to prevent your pet from jumping over a fence and leaving you. Which, if you buy one of these, it will want to do more than ever. From the company's FAQs:

Is it uncomfortable?

Because the Backyard Cat cable is long enough to drag on the ground, it doesn't apply any strain to the cat. The force of dragging is applied along the length of their bodies.

Now listen, just because something isn't physically uncomfortable (although I'm sure this bag is anyways) doesn't mean it isn't uncomfortable in other ways. Take my wedding ring for instance -- it's not really hurting my finger, but the damage it's doing to my life is immeasurable.

Product Page click on 'product' then 'view demo' for the sandbag in action